(1) Field of the Invention
This invention generally relates to an intake door system that efficiently recovers the dynamic pressure in an external flow around a moving vehicle and does not suffer from opening resistance forces generated through pressure recovery in the inlet recess.
(2) Description of the Prior Art
In the current art for submarine torpedo launch systems designs (as generally shown in FIG. 1), a high efficiency inlet 100 is included at an intake side of the system. This inlet 100 includes a recess 102, an intake duct 104 and a hinged door 106. The door 106 is designed so that when it is opened, the dynamic pressure of the mean flow is channeled directly into the intake  duct 104. This pressure is intended to assist a turbine pump 118 in launching a torpedo 116 from a torpedo tube 108.
The basic operation of the type of launch system shown in FIG. 1 is as follows. The inlet door 106, a slide valve 110, and a shutterway recess 112 are opened to create an open flow path through the launch system. Prior to launch, the pressure in the inlet recess 102 and the pressure in the shutterway recess 112 each independently increase to some fraction of the available dynamic head, as a result of forward motion of the platform. Any imbalance in the pressure in these two recesses 102, 112 causes fluid in the launch system, and any device, such as torpedo 116, in the torpedo tube 108, to begin to move. When launch is initiated, the turbine pump 118 begins to rotate and fluid is drawn through the inlet door 106, the inlet recess 102, and the intake duct 104 and into the turbine pump 118. The turbine pump 118 forces fluid into an impulse tank 114 housing the slide valve 110, through the slide valve 110, down the torpedo tube 108 and thereby carrying the weapon 116 in the torpedo tube 108 through the shutterway recess 112 and out of the platform.
In practical systems, the inlet door 106, when fully open, does not effectively direct the external dynamic pressure into the intake duct 104. A second problem is that when the inlet door 106 just begins to open, the dynamic pressure is effectively channeled into the inlet recess 102. This pressurizes a back or rear side of the inlet door 106, preventing it from fully  opening. FIG. 2 shows further detail of this known type of inlet 100 and illustrates the basic back-pressure problem with arrows 120.
The following patents, for example, disclose various inlet systems and arrangements:                U.S. Pat. No. 4,378,097 to Ferguson et al.;        U.S. Pat. No. 4,620,679 to Karanian;        U.S. Pat. No. 5,033,693 to Livingston et al.;        U.S. Pat. No. 5,078,341 to Bichler et al.;        U.S. Pat. No. 5,088,660 to Karanian;        U.S. Pat. No. 5,116,251 to Bichler et al.; and        U.S. Pat. No. 6,264,137 to Sheoran.        
Specifically, Ferguson et al. disclose a smooth surfaced, submerged air inlet for use generally forwardly of an engine in an aircraft (missile or other air vehicle). The inlet has an opening having wall surfaces adapted to be flush with or inwardly of an aircraft body surface. The wall surfaces of the opening have a leading and outer end in a plane and the surfaces extend inwardly to form an uncovered shallow channel-shaped portion to the inlet, the channel portion deepening inwardly in the trailing direction and continuing into a partial ellipse portion of the opening. The ellipse portion deepens inwardly as it extends in a trailing direction and has substantially parallel wall surfaces extending outwardly of the ellipse in the direction toward the level of the plane. There are extensions of said substantially  parallel wall surfaces diverging outwardly to said plane. There is an inwardly trailing surface, spaced outwardly from the partial ellipse portion, being joined to the substantially parallel wall surfaces to form an outer cover for a trailing part of said inlet and of said partial ellipse portion. The inlet, including the cover, trails inwardly and is contoured radially as it trails to form a substantially circular wall surface at its inner end.
The patent to Karanian '679 discloses a two-dimensional inlet for a high speed ram jet missile and includes in combination an educated slot and a single ramp for varying the geometry of the inlet.
Livingston et al. discloses an inlet having a single-piece, flexible inlet ramp skin. A corrugated member is rigidly coupled to the interior surface of the ramp skin to hold the skin rigid in one direction but permit it to be extremely flexible in a second direction. A plurality of beams extends perpendicular to the ridges and grooves of the corrugated member to hold the skin in position in the second direction. Mechanical actuators are coupled to the beams for applying force to vary the shape of the beams and thus the shape of the ramp skin. The inlet area is varied as the ramp skin is moved. The beam member and ramp skin are elastically deformable from an intermediate position in a first direction to increase the area of the inlet and in a second direction to decrease the area of the inlet. Shaping the beam  and ramp skin to be at an intermediate position when not deformed permits a greater range of movement and a more variable inlet area for a given material and weight.
Bichler et al. '341 disclose a hydraulically-pivotable inlet ramp with a box-like shaped cross-section for supplying air into engines of supersonic or hypersonic airplanes. The inlet ramp, comprised of a plurality of relatively movable elements, can be adjusted into a number of different positions to optimize air flow under various mach conditions, as well as control a boundary air layer inlet.
The patent to Karanian '660 discloses a supersonic inlet flow duct provided with a pivoting bleed stability door and biasing spring. The door opens under the influence of increased static fluid pressure behind a shock front, which is displaced forwardly by a downstream pressure perturbation. The opened door diverts portions of the inlet duct flow stabilizing the shock front and downstream shock train within the duct until the perturbation subsides.
Bichler et al. '251 disclose an inlet system, which can be used for all supersonic or hypersonic engine inlets and comprises two or several separate parallel ducts, which must be switched over in specific phases of flight. This is accomplished with a duct shaped parallel inlet element pivotably assigned to the inlet ramp of the inlet, which as a channel-connecting re-direction member alternately can close off the turbo-jet inlet  duct as well as also the ramjet inlet. Preferably, the construction comprises a plurality of pivotably connected box-like elements interconnected in a movable manner.
The patent to Sheoran discloses an air inlet assembly for bringing air to an auxiliary power unit mounted in the compartment of an aircraft. The assembly includes a duct extending from an intake contoured to conform to the aircraft fuselage to an exit coupled to the inlet plenum of the auxiliary power unit. A first door hingeably mounted to the aft side of said intake and moveable from an open position to a closed position where said first door lies flush against intake, said first door having a closing wall and two side walls and a second door hingeably mounted to the forward end of said intake, said second door having a plate with two inwardly extending walls, each of said inwardly extending walls hinged to one of said side walls so that the second door rotates with said first door. During ground operation, air that would have swirled around the side walls of the first door thus generating inlet corner vortices are now blocked by the side walls of the second door.
It should be understood that the present invention would in fact enhance the functionality of the above patents by providing a high efficiency inlet that can be easily opened under dynamic conditions. 